Nokea
Which of the following best describes bacterial conjugation?
- A. Transfer of DNA through a sex pilus
- B. Uptake of free DNA from the environment
- C. Transfer of DNA by bacteriophages
- D. Binary fission
Correct Answer: A
Rationale: The correct answer is A because bacterial conjugation involves the transfer of genetic material through a sex pilus from a donor bacterium to a recipient bacterium. This process allows for the exchange of genetic material and can lead to increased genetic diversity within bacterial populations.
Option B is incorrect because the uptake of free DNA from the environment is known as transformation, not conjugation. Option C is incorrect as transfer of DNA by bacteriophages is called transduction, not conjugation. Option D is incorrect because binary fission is a form of asexual reproduction in bacteria, not a mechanism for genetic exchange.
You may also like to solve these questions
A patient with a severe sore throat had a throat smear revealing Gram-positive cocci in pairs with a capsule. What is the most likely causative agent?
- A. Streptococcus pneumoniae
- B. Staphylococcus aureus
- C. Neisseria meningitidis
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. The presence of Gram-positive cocci in pairs with a capsule is characteristic of Streptococcus pneumoniae. This bacterium is a common cause of bacterial pharyngitis, leading to a severe sore throat. Staphylococcus aureus (B) does not typically present in pairs or have a capsule. Neisseria meningitidis (C) is a Gram-negative diplococcus, not a Gram-positive cocci. Klebsiella pneumoniae (D) is a Gram-negative bacillus, not a cocci. Thus, based on the characteristics described in the question, Streptococcus pneumoniae is the most likely causative agent.
The cytoplasmic membrane of the eukaryotes, in contrast to the one of prokaryotes, has:
- A. cellulose
- B. starch
- C. chitin
- D. sterols
Correct Answer: D
Rationale: The correct answer is D: sterols. Eukaryotic cytoplasmic membranes contain sterols, such as cholesterol, which provide stability and regulate fluidity. This is a key characteristic that distinguishes them from prokaryotic membranes. Cellulose (A) is a component of plant cell walls, not the cytoplasmic membrane. Starch (B) is a carbohydrate used for energy storage in plants. Chitin (C) is a component of fungal cell walls and arthropod exoskeletons, not found in eukaryotic cytoplasmic membranes.
Binary fission is a form of reproduction used by
- A. viruses.
- B. bacteria.
- C. fungi.
- D. helminths.
Correct Answer: B
Rationale: Binary fission is a form of asexual reproduction where a single organism divides into two equal parts. Bacteria reproduce through binary fission, splitting into two identical daughter cells. Viruses are not considered living organisms and reproduce by infecting host cells. Fungi reproduce through spores or sexual reproduction. Helminths are parasitic worms that reproduce sexually. Therefore, the correct answer is B, bacteria, as they specifically utilize binary fission for reproduction.
Fossils of prokaryotes go back __________ billion years.
- A. 4.0 to 5.0
- B. 3.5 to 4.0
- C. 2.5 to 3.0
- D. 2.2 to 2.7
Correct Answer: B
Rationale: The correct answer is B: 3.5 to 4.0 billion years. Prokaryotic fossils date back to around 3.5 to 4.0 billion years ago, based on scientific evidence. This timeframe aligns with the earliest known evidence of life on Earth. Choices A, C, and D have incorrect timelines that do not correspond to the established age range of prokaryotic fossils. Choice A is too broad and includes a range that extends beyond the known fossil record. Choices C and D have much younger timelines, which do not match the historical evidence of prokaryotic life dating back billions of years.
Which bacteria produce urease enzyme to neutralize stomach acid?
- A. Salmonella typhi
- B. Escherichia coli
- C. Helicobacter pylori
- D. Shigella flexneri
Correct Answer: C
Rationale: Rationale:
1. Helicobacter pylori is known for producing urease enzyme to neutralize stomach acid.
2. Urease enzyme converts urea into ammonia, buffering the acidic pH.
3. This adaptation allows H. pylori to survive in the acidic environment of the stomach.
4. Salmonella typhi, Escherichia coli, and Shigella flexneri do not produce urease.
5. Therefore, C is the correct answer based on the unique urease-producing capability of H. pylori.